To change your current or existing MAC address in ubuntu 9.04 just follow the follwing steps.... hope yours will be changed..

1. Open The terminal [Application-->Accessories-->Terminal]2. Write the quoted code or copy and paste it in terminal [without the "" symbols]"sudo gedit /etc/init.d/bootmisc.sh"give sudo password when prompted.3. A file will be opened. In that file after the last line write the following codes or paste it.